The Falcons will aim to bounce back from a disappointing 2013 season this year, and while there are several reasons for optimism, the team’s 2014 chances sustained a significant blow yesterday, when word broke that linebacker Sean Weatherspoon ruptured his Achilles tendon and will be out for the season.

Already a key contributor on defense for Atlanta, Weatherspoon may have assumed even greater importance this year, as the Falcons transition from a 4-3 base defense into a hybrid system that will incorporate more 3-4 looks. With Weatherspoon out of the picture, the pressure is on the remaining linebackers to fill his role, and it’s not an overwhelmingly deep group. The club is currently carrying 11 linebackers on the roster, but seven of those are rookies — either mid-to-late round draft picks or undrafted free agents.

If more linebacker snaps are necessary in the Falcons’ new defensive system though, Atlanta will need to rely on more than those three players to get by. Kroy Biermann is the other returning player on the unit, but he’s coming off a serious Achilles injury of his own, and it remains to be seen whether he’ll be fully returned to form. In some looks, the Falcons may line up 4-3 defensive ends such as Osi Umenyiora as 3-4 outside linebackers — still, the team will likely rotate players in and out of those spots depending on the situation.

Of the first-year players, Notre Dame’s Prince Shembo was the highest pick, selected in the fourth round at No. 139 overall. That doesn’t necessarily mean he’ll be the player to make the most impact right away, but besides Shembo and fifth-rounder Marquis Spruill, all of the Falcons’ rookie LBs were seventh-round picks or undrafted free agents — that suggests most teams, including Atlanta, probably didn’t view those players as ready to step in as immediate contributors. Nonetheless, perhaps one or two players of a group that also includes Yawin Smallwood, Tyler Starr, Brenden Daley, Walker May, and Jacques Smith will provide unexpected production right away.

If the Falcons aren’t comfortable with their internal options, exploring free agency is an alternative. Although most impact players were snatched up months ago, linebacker is one spot where there are still a few notable names on the board. Jeff Schultz of the Atlanta Journal-Constitution suggests James Harrison is one player for the club to consider, while ESPN.com’s Vaughn McClure wonders if Dan Connor, who worked out for Atlanta earlier in the offseason, is worth a longer look.

A glance at our list of remaining free agents reveals a few other possibilities. Pat Angerer and Jonathan Vilma are among the veterans who could have some value, and there are a pair of former Falcons still on the market as well, in Omar Gaither and Stephen Nicholas. Considering the team is implementing a new defensive system, the fact that Gaither and Nicholas played in Atlanta last year wouldn’t necessarily be a huge plus, though at least the Falcons have first-hand familiarity with those players’ strengths and weaknesses.

Ultimately, the Falcons may be content to see how their rookies and returning linebackers fare in Weatherspoon’s absence. However, considering how Atlanta’s defense performed in 2013, entering the 2014 campaign with a similar group of players at the LB position has to give the team pause. I’d expect the Falcons to peruse the free agent market with a little more urgency before training camp in search of a potential upgrade.